01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving an overhang for easy removal.
02 - Whisk together melted butter and granulated sugar in a large bowl. Add eggs, vanilla extract, and red food coloring. Mix until smooth.
03 - Sift in cocoa powder, flour, and salt. Fold gently until just combined—do not overmix.
04 - Reserve 1/4 cup of the brownie batter. Pour the remaining batter into the prepared pan, smoothing the top.
05 - Beat cream cheese until smooth in a medium bowl. Add sugar, egg yolk, and vanilla extract, mixing until creamy.
06 - Drop spoonfuls of the cheesecake mixture over the brownie base. Add small dollops of the reserved red velvet batter on top. Using a skewer or knife, gently swirl the batters to create a marbled effect.
07 - Bake for 33–36 minutes, until the center is just set and a toothpick comes out with a few moist crumbs.
08 - Cool completely in the pan before lifting out and slicing into squares.